Lighting system including electrical discharge tubes



July 5, 1938.

M. PIRANI El AL 36 LIGHTING SYSTEM INCLUDING ELECTRICAL DISCHARGE TUBESmvram'ows MarceHo Pircmi glari'in Re er- A TORNEY Patented July 5, 1938LIGHTING SYSTEM INCLUDING ELECTRI- CAL DISCHARGE TUBES Marcello Piraniand Martin Rcger, Berlin, Germany, assignors to General ElectricCompany, a corporation of New York Application March 31, 1936, SerialNo. 71,880 In Germany April 1, 1935 1 Claim.

ing systems including electrical discharge tubes,

and more particularly in systems in which the lighting tubes have asupply of alternating our- 5 rent or intermittent direct current. Insuch systems the light intensity is reduced whenever the alternatingcurrent passes through zero or the intermittent current is interrupted,which is objectionable for many purposes. It has heretofore beenproposed to superpose a high frequency or high voltage component on thecircuit of the tube. While such systems cause an earlier ignition andthereby a reduction of the space of reduced light intensity in eachperiod of the current, yet the said space is not completely filled out.Further, it has been proposed to superpose a constant direct current inorder to prevent the light intensity from being reduced to zero in eachperiod. But in this system the variation of the light intensity of thetube is not reduced, because the curve of the light intensity is changedonly as to its distance from the axis of abcissae, while its form isnot' altered. Further, the operation of the system is complicated andexpensive because means for supplying direct current must be provided inaddition to the source of alternating or intermittent current. Finallyit has been proposed in multi-phase currents to bridge the said spacesby phase displacement and by using several electrodes. However, thismethod is effective only where three phase current is used, while thecurve of the light intensity is-still wavy where only two tubes ofdiiferent phase are used, and therefore in this case only a glimmeringlight is obtained.

The object of the improvements is to provide a system of the classindicated and comprising a lighting tube charged with alternatingcurrent or with intermittent direct currentwhich emits a light which issteady, and with this object in view our invention consists in chargingthe tube with an additional current the phase of which is displacedrelatively to the phase of the main current, the said current beingtransformed into intermittent current impulses which .are adapted toproduce a light emission which is complementary to the light emission ofthe main current, and which therefore exactly fills out the dark spacesintermediate the light emission periods of the tube, the result beingthat the curve of the light intensity is the same as. that of acontinuous current.

For the purpose of explaining the invention an example embodying thesame has been shown in the accompanying drawing in which the same (Cl.176-124) Our invention relates to improvements in lightreferencecharacters have been used in all the views to indicate correspondingparts. In said drawing,

Fig. 1 is a diagram showing the light emission of a tube charged withsinusoidal alternating current and the light emission produced bysubsidiary or superposed current impulses, and

Fig. 2 is a diagrammatical view showing the lighting tube and theelectrical connection thereof.

As is shown in Fig. 1 the curve a of the intensity of the light emittedfrom a tube charged with the sinusoidal alternating current of 50periods comprises successive periods of light emission and dark spaces.The curve b shows the light emission of a subsidiaryalternating currentthe phase of which is displaced with relation to that of the maincurrent, and which is shaped so as to produce comparatively shortcurrent impulses, the period and the shape of the curve I) being exactlycomplementary to the shape of the curve a, so that by addition of thesaid curves a line is obtained which is straight and parallel to thezero axis. Therefore in service the tube has uniform light intensitywhich is independent of the oscillationsof the alternating current andit emits a perfectly steady light.

.As is shown in Fig. 2, the lighting tube 2 is provided with twoelectrodes I which are connected in a main circuit l2 including a sourceof alternating current 3 and a choking coil 4. Further, the main circuitl2 includes the secondary 5 of a transformer B, the primary 1 of whichis included in a subsidiary circuit l3 which is connected to a source ofalternating current 8. The phase of the alternating current suppliedfrom the source 8 is displaced with relation to the phase of thealternating current supplied by the source 3 so that current impulsesare produced in the circuit l3 during the dark porcircuit l3 includes aresistance 9, and connected in shunt to the priinary 1 there is acondenser, l0 and a cathode glow lamp II. By the alternating currentsupplied from the source 8 the condenser and the cathode glow lamp arecharged up to the ignition voltage of the glow lamp, and thereafter thecathode glow lamp is ignited, and the quantity of electricity stored inthe condenser is delivered, so that the voltage at the ends of theprimary 1 of the transformer 6 is reduced. By this sudden reduction ofthe voltage a current impulse is induced in the secondary of thetransformer which is supplied to the lighting tube 2 through thesecondary 5, the said current impulse being displaced in phaserelatively to the main alternating current supplied from the source 3.By providing a resistance 9, a condenser ID, a cathode glow lamp II anda transformer 6 of the proper dimensions a current impulse is producedin each half wave of the subsidiary current which exactly corresponds asto shape and intensity to the dark spaces of thelight emission producedby the main current, and which completes the curve of the light emissionto a straight line.

While in describing the invention reference has been made to specificmeans for producing a superposed alternating current of different phase,we wish it to be understood that our invention is not limited to thesaid means. Further, we wish it to be understood that we do not limitourselves to a construction in which the secondary 5 is connected to themain electrodes I, and that separate subsidiary electrodes may beprovided for the secondary, of the transl former.

We claim:

An illuminating system comprising in combi- 5 9 nation, a gaseouselectric discharge lamp device, means for supplying a main current ofvarying intensity to said device to cause said device to emit light ofvarying intensity and means for supplying a subsidiary current to saiddevice 10 which current is displaced in plase *with respect to said maincurrent, and'which is capable of causing said device to produce lightwhich is complementary to the light caused by the main current in saiddevice, and completes the curve of 15 the light emission of the deviceto a straight line, said last named means comprising a transformerhaving the secondary thereof connected inseries with said lamp deviceand the primary thereof connected across the terminals of an alternating20 of said cathode glow lamp being less than the potential supplied bysaid current source.

MARCELLO PIRANI. MARTIN REGER.

